Lateral Root Initiation in Cucumber (): What Does the Expression Pattern of () Tell Us?

In Arabidopsis, the small signaling peptide (peptide hormone) RALF34 is involved in the gene regulatory network of lateral root initiation. In this study, we aimed to understand the nature of the signals induced by RALF34 in the non-model plant cucumber (), where lateral root primordia are induced in the apical meristem of the parental root. The RALF family members of cucumber were identified using phylogenetic analysis. The sequence of events involved in the initiation and development of lateral root primordia in cucumber was examined in detail. To elucidate the role of the small signaling peptide RALF34 and its receptor THESEUS1 in the initial stages of lateral root formation in the parental root meristem in cucumber, we studied the expression patterns of both genes, as well as the localization and transport of the RALF34 peptide. is expressed in all plant organs. seems to differ from in that its expression is not regulated by auxin. The expression of as well as is regulated in part by ethylene. is expressed constitutively in cucumber root tissues. Our data suggest that RALF34 acts in a non-cell-autonomous manner and is not involved in lateral root initiation in cucumber.